The present invention relates to cassettes which contain a magnetically affixable printing tape.
Conventionally, tape printers are widely used which print a character string on a printing tape and which cut a printed portion from the printing tape to produce a label.
Tape cassettes used in the printers contain a pair of reels around which a printing tape and an ink ribbon are wound, respectively. The printing tape includes a printing layer of a resin film with an adhesive layer coated on its side and a separable paper strip adhered to the printing layer through the adhesive layer. The tape cassette is set on the tape printer and feeds the printing tape and the ink ribbon to a printing section.
The label produced by the tape printer can be pasted on a desired object by separating its separable paper piece therefrom. Once pasted on the object, the label cannot be easily separated from the object because it strongly adheres to the object.
A magnet sheet is known, from which a smaller sheet piece of a desired size is obtained. Appropriate characters are handwritten on the smaller sheet piece, which is then affixed magnetically, for example, to a white board of steel or another magnetic object for use.
However, the conventional magnet sheet is not composed in consideration of printing in the tape printer and is not suitable for printing. Thus, tape-like magnet materials are desired from which labels are obtained on the tape printer. The inventors have made a series of studies to put to a practical use magnetically affixable printing tapes on which characters/images are printable by the tape printer.
First, in order that the magnetically affixable printing tape may be used in the tape printer like the conventional printing tape with an adhesive on its side, a magnetically affixable printing tape consisting of a printing layer and a magnetic layer pasted to the printing layer is required to be wound around a reel, and a resulting roll of the printing tape is required to be accommodated within a cassette. Since the printing tape is wound repeatedly around the reel in a superimposing manner, there may occur a trouble, for example, with conveyance of the tape depending on a magnetic pole arrangement pattern formed on the tape, as we have found. For example, a magnet sheet has magnetized lines along which the S and N poles of a particular width alternately arranged extend. A magnetically affixable tape is required to be produced appropriately from the magnet sheet by paying careful attention to the magnetized lines. If otherwise, a trouble can occur when a roll of such tape is accommodated within the tape cassette and characters/images are then printed on a tape portion fed out from the cassette.
Specifically, when the magnetically affixable printing force tape is magnetized widthwise thereof, S and N poles which extend widthwise thereof are alternately arranged longitudinally of the tape. When this tape is wound around its holding reel in superimposing relationship, the respective turns of the tape differ in diameter. Thus, poles of adjacent turns of the tape which can overlap can have the same or a different polarity depending on their winding diameters. Thus, when a force fluctuates which is required for drawing our the printing tape from the tape cassette to feed the tape to the printing section. Especially, when the radially overlapping magnetic poles of adjacent turns of the tape have the same polarity, a very large drawing force is required. In the tape printer, a conveying step motor drives the platen roller to convey the printing tape lengthwise at constant speeds while heaters of the thermal head arranged widthwise of the tape are driven to print characters/images a line at a time. When the force required for drawing the printing tape from its cassette increases to some extent, a slip can occur between the platen roller and the printing tape and the conveyance of the printing tape becomes unstable to thereby cause bad printing such as is due to a reduction in the space between the printing lines.
When the printing tape is wound around a holding reel, a magnetic layer of one turn of the tape is brought into contact with a back of a printing layer of the adjacent turn. In this case, small particles or grains of the magnetic layer, which contains a mixture of a synthetic resin or synthetic rubber and magnetic powder, would move to a surface of the printing tape to soil the same, as we found. A printer of this type generally employs a heat-transfer printing system. When inks of the conventional ink ribbon are not supposed as being used to print characters on the printing tape, characters/images printed on the tape would be blurred, which is a new problem.
The ink ribbon consists generally of a base film of capacitor paper, glassine or a resin film of polyester or a polyimide resin, and an ink layer coated on the base film. The ink layer includes a mixture of a wax or resin and a coloring agent such as a pigment. When an ink of the ink layer is transferred to the printing medium, a luster occurs on a surface of the ink-transferred to the printing medium, especially in the heat transfer system. In order to suppress this luster, a luster suppressing additive is added into the ink layer or a luster control layer is provided between the base film and the ink layer.
In many cases, a pigment added as a coloring agent to the ink layer is, for example, carbon black or an iron oxide in the case of a black ink. Similarly, the luster control layer contains an iron oxide pigment for delustering.
We also have found in a test for putting the tape to practical use that the "blurs" of the characters printed on the printing tape are due to exertion of the magnetic drawing force of the magnetic layer on the iron oxide pigment contained in the ink layer/luster control layer.
When once a label produced from the magnetic tape is affixed magnetically to a magnetic object, it is difficult to separate the former from the latter.
When the magnetically affixable printing tape contained in the tape cassette is used substantially up to its end, a small end portion of the tape is likely to remain in, be drawn against, the printer and enter a space in the printer and is difficult to remove.